if exists(
SELECT 
*
FROM sys.objects so
INNER JOIN sys.schemas s ON s.[schema_id] = so.[schema_id]
INNER JOIN sys.[columns] c ON c.[object_id] = so.[object_id]
INNER JOIN sys.extended_properties ep ON ep.major_id = so.[object_id] AND c.column_id = ep.minor_id AND ep.Name = 'MS_Description'
WHERE so.Type_Desc = 'USER_TABLE' AND so.Name <>'sysdiagrams'
AND s.Name ='{1}'
AND so.name ='{2}'
AND c.name ='{3}' 
)
EXEC sp_dropextendedproperty 
@name = N'MS_Description', 
@level0type = N'Schema', @level0name = '{1}',
@level1type = N'Table',  @level1name = '{2}',
@level2type = N'Column', @level2name = '{3}';

--if len('{0}') >0
EXEC sp_addextendedproperty 
@name = N'MS_Description', 
@value = '{0}',
@level0type = N'Schema', @level0name = '{1}',
@level1type = N'Table',  @level1name = '{2}',
@level2type = N'Column', @level2name = '{3}';